Wireless Power Systems with Shared Inductive-Loss Scaling Factors

This application is a continuation of U.S. patent application Ser. No. 17/681,363 filed Feb. 25, 2022, which claims the benefit of provisional patent application No. 63/167,971, filed Mar. 30, 2021, which is hereby incorporated by reference herein in its entirety.

This relates generally to power systems, and, more particularly, to wireless power systems for charging electronic devices.

In a wireless charging system, a wireless power transmitting device wirelessly transmits power to a wireless power receiving device. The wireless power transmitting device uses a wireless power transmitting coil to transmit wireless power signals to the wireless power receiving device. The wireless power receiving device has a coil and rectifier circuitry. The coil of the wireless power receiving device receives alternating-current wireless power signals from the wireless power transmitting device. The rectifier circuitry converts the received signals into direct-current power.

Wireless power transmitting devices may transmit wireless power to wireless power receiving devices. In each wireless power transmitting device, an inverter and wireless power transmitting coil are used to transmit wireless power signals. Wireless power receiving devices may be magnetically coupled to wireless power transmitting devices so that power may be transferred from the transmitting devices to the receiving devices. In each wireless power receiving device, wireless power signals from a paired transmitting device are received using a wireless power receiving coil. A rectifier in the wireless power receiving device rectifies alternating-current signals from the wireless power receiving coil and produces corresponding direct-current power.

Power loss calculations may be used to help determine whether a foreign object might be present in the vicinity of a coupled wireless power transmitter and receiver. If an estimated foreign object power loss value is determined to be below a predetermined threshold, wireless power transfer operations may proceed normally. If, however, an estimated foreign object power loss value is determined to be above the predetermined threshold, it can be concluded that a foreign object is present and normal power transfer operations may be halted or otherwise forgone.

In an ecosystem with multiple models of transmitter and multiple models of receiver, scaling factors may be maintained by the transmitters and receivers. These scaling factors may be exchanged between the transmitter and receiver in a coupled transmitter-receiver pair to allow accurate power loss estimates to be made.

Ecosystem scaling techniques can also be used more generally, for example, to adjust runtime models of other types in a coupled system such as a system with multiple types of transmitters and receivers. This can be useful for any algorithm which depends on these models to calculate properties in a mated system. As examples, ecosystem scaling can be used in wireless power transfer systems in estimating the coupling between a transmitter and receiver or in estimating the maximum power delivery or coil-to-coil efficiency of power delivery. In general, any ecosystem with different possible permutations of mated devices may exchange scaling factors and/or other parameters at runtime to enable an accurate coupled model for the mated devices.

A wireless power system includes a wireless power transmitting device. The wireless power transmitting device wirelessly transmits power to a wireless power receiving device. The wireless power transmitting device may be a charging puck, a charging mat, a portable electronic device with power transmitting capabilities, a removable battery case with power transmitting capabilities, or other power transmitter. The wireless power receiving device may be a device such as a wrist watch, cellular telephone, tablet computer, laptop computer, removable battery case, electronic device accessory, or other electronic equipment. The wireless power receiving device uses power from the wireless power transmitting device for powering the receiving device and for charging an internal battery.

Wireless power is transmitted from the wireless power transmitting device to the wireless power receiving device by using an inverter in the wireless power transmitting device to drive current through one or more wireless power transmitting coils. The wireless power receiving device has one or more wireless power receiving coils coupled to rectifier circuitry that converts received wireless power signals into direct-current power.

If a foreign object such as a paperclip, coin, or other metallic object is present near the wireless power transmitting coil of the wireless power transmitting device, there may be eddy current generation in the foreign object that could increase its temperature. To determine whether a foreign object is present in the vicinity of the wireless power transmitting device, power loss estimates are made. For example, the amount of power loss in the transmitter and the amount of power loss in the receiver are estimated. By comparing the measured output power from the rectifier circuitry to the amount of input power to the inverter and by subtracting estimated transmitter and receiver losses, the amount of power that might have been absorbed by a foreign object can be computed. If the estimated foreign object power is higher than a threshold, power delivery can be halted and/or other suitable action taken.

To estimate foreign object power loss values accurately, various potential sources of power loss in a wireless power system should be taken into account. Some power losses exhibited by power transmitters and receivers are independent of the magnetic properties of the transmitters and receivers (e.g., switching losses, losses that depend on the drain-source resistance of field-effect transistors in the inverters and rectifiers, etc.). Losses such as these can be taken into account by characterizing relevant device components (e.g., by ascertaining transistor drain-source resistances using measurements made during manufacturing tests and/or other tests).

Transmitters and receivers also exhibit power losses that depend on the inductive properties of the transmitters and receivers (e.g., losses dependent on the magnetic properties of coupled transmitters and receivers, sometimes referred to as mating-dependent losses, inductive losses, magnetic losses, etc.). Examples of power losses that are dependent on the magnetic properties of the transmitters and receivers include: 1) coil losses that depend on the alternating-current (AC) resistances of mated transmitting and receiving coils, 2) friendly metal losses (e.g., power losses due to eddy currents induced in the metal housing of a receiving device, and 3) foreign object losses that arise in the event that a foreign object is present between a transmitter and receiver. Power losses such as these that are dependent on the magnetic properties of the transmitter and receiver may sometimes be characterized in terms of LQK magnetic parameters, where L refers to the inductance of the transmitting and receiving coils, Q refers to the quality factor of the coils, and K refers to the magnetic coupling of the coils.

In a wireless power ecosystem with numerous different transmitters and receivers, each pairing between a given one of the transmitters and a given one of the receives will result in potentially different set of magnetic properties, thereby posing challenges to accurate assessment of power losses that depend on the magnetic properties of a coupled transmitter-receiver pair. To facilitate accurate transmitter and receiver power loss estimates, the magnetic power loss parameters associated with transmitters and receivers can be determined using measurements between various models of transmitter and receiver and reference units (e.g., reference transmitters and reference receivers). Characterizing information from measurements made with reference transmitters and/or reference receivers can be stored in each different model of device and subsequently used to help ensure accurate power loss estimates are made when a particular model of transmitter is paired with a particular model of receiver.

An illustrative wireless power system (wireless charging system) is shown in. As shown in, wireless power systemincludes a wireless power transmitting device such as wireless power transmitting deviceand includes a wireless power receiving device such as wireless power receiving device. Wireless power transmitting deviceincludes control circuitry. Wireless power receiving deviceincludes control circuitry. Control circuitry in systemsuch as control circuitryand control circuitryis used in controlling the operation of system. This control circuitry may include processing circuitry associated with microprocessors, power management units, baseband processors, digital signal processors, microcontrollers, and/or application-specific integrated circuits with processing circuits. The processing circuitry implements desired control and communications features in devicesand. For example, the processing circuitry may be used in processing user input, handling negotiations between devicesand, sending and receiving in-band and out-of-band data, making measurements, estimating power losses, determining power transmission levels, and otherwise controlling the operation of system.

Control circuitry in systemmay be configured to perform operations in systemusing hardware (e.g., dedicated hardware or circuitry), firmware and/or software. Software code for performing operations in systemand other data is stored on non-transitory computer readable storage media (e.g., tangible computer readable storage media) in control circuitry. The software code may sometimes be referred to as software, data, program instructions, instructions, or code. The non-transitory computer readable storage media may include non-volatile memory such as non-volatile random-access memory (NVRAM), one or more hard drives (e.g., magnetic drives or solid state drives), one or more removable flash drives or other removable media, or the like. Software stored on the non-transitory computer readable storage media may be executed on the processing circuitry of control circuitryand/or. The processing circuitry may include application-specific integrated circuits with processing circuitry, one or more microprocessors, a central processing unit (CPU) or other processing circuitry.

Power transmitting devicemay be a stand-alone power adapter (e.g., a wireless charging mat or charging puck that includes power adapter circuitry), may be a wireless charging mat or puck that is coupled to a power adapter or other equipment by a cable, may be a portable device, may be equipment that has been incorporated into furniture, a vehicle, or other system, may be a removable battery case, or may be other wireless power transfer equipment.

Power receiving devicemay be a portable electronic device such as a wrist watch, a cellular telephone, a laptop computer, a tablet computer, an accessory such as an carbud, a wirelessly charged removable battery case for an electronic device, or other electronic equipment. Power transmitting devicemay be coupled to a wall outlet (e.g., an alternating current power source), may have a battery for supplying power, and/or may have another source of power. Power transmitting devicemay have an alternating-current (AC) to direct-current (DC) power converter such as AC-DC power converterfor converting AC power from a wall outlet or other power source into DC power. DC power may be used to power control circuitry. During operation, a controller in control circuitryuses power transmitting circuitryto transmit wireless power to power receiving circuitryof device. Power transmitting circuitrymay have switching circuitry (e.g., inverter circuitryformed from transistors) that is turned on and off based on control signals provided by control circuitryto create AC current signals through one or more wireless power transmitting coils such as wireless power transmitting coil(s). These coil drive signals cause coil(s)to transmit wireless power. Multiple coilsmay be arranged in a planar coil array (e.g., in configurations in which deviceis a wireless charging mat) or may be arranged to form a cluster of coils (e.g., in configurations in which deviceis a wireless charging puck). In some arrangements, device(e.g., a charging mat, puck, etc.) may have only a single coil. In other arrangements, a wireless charging device may have multiple coils (e.g., two or more coils, 2-4 coils, 5-10 coils, at least 10 coils, fewer than 25 coils, or other suitable number of coils).

As the AC currents pass through one or more coils, alternating-current electromagnetic (e.g., magnetic) fields (wireless power signals) are produced that are received by one or more corresponding receiver coils such as coil(s)in power receiving device. Devicemay have a single coil, at least two coils, at least three coils, at least four coils, or other suitable number of coils. When the alternating-current electromagnetic fields are received by coil(s), corresponding alternating-current currents are induced in coil(s). The AC signals that are used in transmitting wireless power may have any suitable frequency (e.g., 100-400 kHz, etc.). Rectifier circuitry such as rectifier circuitry, which contains rectifying components such as synchronous rectification metal-oxide-semiconductor transistors arranged in a bridge network, converts received AC signals (received alternating-current signals associated with electromagnetic signals) from one or more coilsinto DC voltage signals for powering device.

The DC voltage produced by rectifier circuitry(sometime referred to as rectifier output voltage Vrect) can be used in charging a battery such as batteryand can be used in powering other components in device. For example, devicemay include input-output devices. Input-output devicesmay include input devices for gathering user input and/or making environmental measurements and may include output devices for providing a user with output. As an example, input-output devicesmay include a display, speaker, camera, touch sensor, ambient light sensor, and other devices for gathering user input, making sensor measurements, and/or providing user with output.

Deviceand/or devicemay communicate wirelessly using in-band or out-of-band communications. Devicemay, for example, have wireless transceiver circuitrythat wirelessly transmits out-of-band signals to deviceusing an antenna. Wireless transceiver circuitrymay be used to wirelessly receive out-of-band signals from deviceusing the antenna. Devicemay have wireless transceiver circuitrythat transmits out-of-band signals to device. Receiver circuitry in wireless transceivermay use an antenna to receive out-of-band signals from device. In-band transmissions between devicesandmay be performed using coilsand. With one illustrative configuration, frequency-shift keying (FSK) is used to convey in-band data from deviceto deviceand amplitude-shift keying (ASK) is used to convey in-band data from deviceto device. Power may be conveyed wirelessly from deviceto deviceduring these FSK and ASK transmissions.

Control circuitryhas measurement circuitry. Measurement circuitrymay include voltage measurement circuitry (e.g., for measuring one or more voltages in devicesuch as a coil voltage associated with a wireless power transmitting coil) and/or current measurement circuitry (e.g., for measuring on or more currents such as a wireless power transmitting coil current).

Control circuitryhas measurement circuitry. Measurement circuitrymay include voltage measurement circuitry (e.g., for measuring one or more voltages in devicesuch as a coil voltage associated with a wireless power transmitting coil and/or a rectifier output voltage) and/or current measurement circuitry (e.g., for measuring on or more currents such as wireless power receiving coil current and/or rectifier output current).

shows illustrative wireless power circuitry in systemin an illustrative scenario in which a wireless power transmitting device has been paired with a wireless power receiving device. The wireless power circuitry ofincludes wireless power transmitting circuitryin wireless power transmitting deviceand wireless power receiving circuitryin wireless power receiving device. During operation, wireless power signalsare transmitted by wireless power transmitting circuitryand are received by wireless power receiving circuitry. The configuration ofincludes a single transmitting coiland a single receiving coil(as an example). In other implementations, voltage across capacitoris measured and current through the coil is inferred from that measurement.

As shown in, wireless power transmitting circuitryincludes inverter circuitry. Inverter circuitry (inverter)may be used to provide signals to coil. During wireless power transmission, the control circuitry of devicesupplies signals to control inputof inverterthat cause inverterto supply alternating-current drive signals to coil. Circuit components such as capacitormay be coupled in series with coilas shown in. Measurement circuitryin devicemay make measurements on operating currents and voltages in device. For example, voltage sensorA may be used to measure the coil voltage across coiland current sensorB may be used to measure the coil current through coil.

When alternating-current current signals are supplied to coil, corresponding alternating-current electromagnetic signals (wireless power signals) are transmitted to nearby coils such as illustrative coilin wireless power receiving circuitry. This induces a corresponding alternating-current (AC) current signal in coil. Capacitors such as capacitorsmay be coupled in series with coil. Rectifierreceives the AC current from coiland produces corresponding direct-current power (e.g., direct-current voltage Vrect) at output terminals. This power may be used to power a load. Measurement circuitryin devicemay make measurements on operating currents and voltages in device. For example, voltage sensorA may measure Vrect (the output voltage of rectifier) or a voltage sensor may measure the coil voltage on coil. Current sensorB may measure the rectifier output current of rectifieror a current sensor may measure the current of coil.

The measurements made by measurement circuitryandmay be processed to extract magnetic loss properties (e.g., coefficients or other parameters that characterize the amount of power losses in devicesandand that are dependent on the magnetic properties of the transmitter and receiver). These measurements may be stored within each device and may be exchanged between devices so that device(and, if desired, device) may use this information in accurately estimating any foreign object power loss that might be present.

If desired, these measurements may be used to estimate how well transmitter and receiver are able to transfer wireless power and therefore whether a user is to be informed that wireless power transfer operations are proceeding normally. For example, these measurements may be used to estimate a magnetic coupling coefficient K, wireless power transfer efficiency, estimated foreign object power loss, and/or other attributes of the mated transmitter-receiver pair. In addition to or instead of estimating foreign object power loss to determine whether a foreign object is present and therefore whether to proceed with wireless power transfer, the systemmay use this information (e.g., estimated foreign object power loss and/or related coupling and/or efficiency information) to determine whether to present the user of systemwith a confirmatory message to inform a user that wireless power transmission are proceeding properly (e.g., to inform the user that this process has not been thwarted by the presence of poor coupling due to presence of a foreign object, possible misalignment, or other factors). Exemplary confirmatory messages include audio output such as a chime and/or visual output presented on device. A chime may involve presentation of an audible chime tone and a visual user interface affordance (e.g., a battery charging icon or other visual alert displayed on a display in deviceor other display). By providing the chime, the user is reassured that charging operations are proceeding normally (e.g., so that the user is comfortable walking away from systemand leaving devicesandunattended until charging is complete).

In general, any suitable information may be exchanged between devices in systemand this information may be used in any suitable way. The exchange of measurements such as those made using measurement circuitryandand the use of this information in determining whether a foreign object is present is illustrative.

Following measurements with circuitryand, the amount of power potentially absorbed by a foreign object in systemmay be determined using equation 1.

In equation 1, PFO represents the amount of power absorbed by a foreign object that is present (if any). POUT represents output power (e.g., the output power of rectifier), PIN represents input power (e.g., the input power to coil), PLOSSTX represents power loss attributable to device, and PLOSSRX represents power loss attributable to device. The values of POUT and PIN may be measured (e.g., using circuitryand). Mathematical models may be used to produce functional expressions for PLOSSTX and PLOSSRX and these expressions can be evaluated using measured operating parameter such as the measurements made using circuitryand. For example, with one illustrative modeling embodiment, PLOSSTX and PLOSSRX can be computed using equations 2a and 3a, respectively.

In equations 2a and 3a, ITX represents transmitter current (e.g., coil current) and IRX represents receiver current (e.g., rectifier output current or, in some embodiments, receiver coil current). The values of RAIRTX and RAIRRX represent measured AC coil resistances for coilsandrespectively. The values of b, m, α, and αDC are model parameters (sometimes referred to as magnetic power loss coefficients) that characterize the performance of the coupled transmitter and receiver pair in system. Transmitter power loss PLOSSTX is solely due to transmitter coil power loss in the model of equation 2a. Receiver power loss PLOSSRX has a first component that is due to receiver coil power losses (the first term of equation 3a) and has a second component (made up of the last two terms in equation 3a) that represents friendly metal losses (e.g., losses due to eddy currents induced in the receiver when power is being transferred). Parameter b may sometimes be referred to as transmitter coil loss parameter or coefficient. Parameter m may sometimes be referred to as a receiver coil loss parameter or coefficient, and parameters α and αDC may sometimes be referred to as friendly metal loss parameters or friendly metal loss coefficients. Parameters b, m, α, and αDC depend on the magnetic interactions between deviceandwhen coupled and may therefore sometimes be referred to as magnetic loss parameters or magnetic loss coefficients.

In an ecosystem in which there are multiple different models of wireless power transmitting device available to a user (e.g., different models of device) and multiple different models of wireless power receiving device available to the user (e.g., different models of device), the magnetic loss parameters will vary as a function of which particular transmitter and receiver are paired together. If, as an example, a model I transmitter and model J receiver are paired, the amount of power loss in each device will differ from that experienced when these devices are paired with different devices.

To account for these variations and thereby ensure accurate estimation of foreign object power loss in equation 1, magnetic power loss parameter scaling factors (sometimes referred to as magnetic power loss coefficient scaling factors) are used. In particular, the models of PLOSSTX and PLOSSRX of equations 2a and 2b, which may be inaccurate in ecosystems with multiple different transmitter and receiver models, may be replaced by equations 2b and 3b, respectively.

In equation 2b, the transmitter coil loss parameter b is replaced by a reference transmitter coil loss value bR (sometimes referred to as a transmitter coil loss coefficient) that is associated with the transmitter loss measured when a reference transmitter is coupled to a reference receiver and this value is then scaled using the scaling factor gb. In equation 3b, the receiver coil loss parameter m is replaced with mR (sometimes referred to as a receiver coil loss coefficient), which is associated with the receiver coil loss measured when a reference receiver and transmitter are coupled, and this value is then scaled using the scaling factor gm. In equation 3b, the friendly metal loss parameters α and αDC are replaced respectively with reference friendly metal loss parameters (coefficients) αR and αRDC extracted using measurements made with a reference transmitter and reference receiver. The reference friendly metal loss parameters are scaled by respective scaling factors gα and gαDC.

By using scaling factors in computing PLOSSTX (see, e.g., equation 2b) and PLOSSRX (see, e.g., equation 3b), equation 1 can be satisfactorily evaluated regardless of which models of transmitter and receiver are paired with each other.

Illustrative operations involved in using measuring transmitters and receivers to determine their scaling parameters are shown in the flow chart of. Operations inare performed at design time and the resulting scaling factors are stored in production units. Illustrative operations involved in using the scaling parameters in systemare shown in. Operations inare performed at runtime (e.g., when transmitter and receiver are paired in preparation for transmitting wireless power between transmitter and receiver). In the examples of, it is assumed that the scaling factors for a particular model of transmitter (a model I transmitter) and a particular model of receiver (e.g., a model J receiver) are being obtained using reference device measurements and then subsequently used when a model I transmitter is paired with a model J receiver. In general, this process is expected to be performed for numerous models of transmitter (models other than model I) and for numerous models of receiver (models other than model J). Moreover, any of the various different models of transmitter that have been characterized may, in general, be paired by a user with any of the various different models of receiver that have been characterized. This is because not all users own the same model of transmitter and not all users own the same model of receiver. In the present example, an illustrative user pairs a model I transmitter with a model J receiver during the operations of.

Operations involved in measuring magnetic power loss parameter scaling factors for a model I transmitter and model J receiver are shown in. During the operations of block, a reference wireless power receiving device is paired (physically or via a simulated pairing such as a finite element analysis simulation pairing) with a reference wireless power transmitting device. Physical reference devices may be obtained from a centralized source or may be constructed by different device manufacturers in accordance with a universally distributed reference design. Once paired, the reference transmitter and reference receiver may begin transferring power. In particular, during the operations of blockthe reference transmitter may send wireless power signals to the reference receiver while internal operating parameters (e.g., transmitter and receiver currents and voltages) are measured and stored. From these measurements, the reference magnetic loss parameters are extracted (e.g., the values of reference magnetic loss parameters bR, mR, αR, and αRDC are obtained). In scenarios in which pairing simulations are used in place of measurements on physically paired devices, finite element analysis simulation is used to determine the LQK of the coupled transmitter-receiver pair and then circuit simulations are used to determine the expected currents and voltages. These simulated currents and voltages can then be used to determine the magnetic loss parameters.

After the reference magnetic loss parameters have been determined (either by physical measurements or simulations), a model J receiver is paired with a reference transmitter. While these devices are paired in a simulation or while these devices are physically paired and wireless power is being transferred from the reference transmitter to the model J receiver, loss parameter measurements for the model J receiver may be obtained. In particular, during the operations of block, the model J loss parameters (coefficients) bRj, mRj, αRj, and αRjDC are obtained. The “J” in each of these parameters and the R (for “reference”) in each of these parameters indicates that the loss parameters are specific to a scenario in which a model J receiver is operating with a reference transmitter. The scaling factor gb (equation 2b) for the model J receiver can then be computed using equation 4 and stored in all model J wireless power receiving devices (e.g., during manufacturing or later using an update).

During the operations of block, a model I transmitter is paired with a reference receiver. Power is transmitted wirelessly while transmitter operating parameters (e.g., currents and voltages) are measured. From these measurements or simulations, magnetic loss parameters miR, biR, αiR, and αiRDC are obtained for the model I transmitter. Using equations 5, 6, and 7, the scaling factors gm, gα, and gαDC for the model I transmitter are then calculated.

The scaling factors for the model I transmitter are then stored in all model I transmitters (e.g., during manufacturing or later using an update).

Illustrative operations involved in using the scaling factors for a model I transmitter and a model J receiver in a scenario in which a model I transmitter and model J receiver are paired by a user are shown in the flow chart of.

During the operations of, a user with a model J receiver and a model I transmitter who wishes to wirelessly transfer power from the model I transmitter to the model J pairs the model I transmitter and model J receiver during the operations of block(e.g., by magnetically attaching a model I charging puck to a model J cellular telephone, as just one example).

During the operations of block, the model I transmitter and model J receiver exchange information such as their scaling factors (e.g., using low-power in-band communications or other wireless communications) and being to transfer power. For example, the model J receiver sends the value of scaling factor gm that was obtained from the model J measurements with the reference transmitter at blockofto the model I transmitter. The model I transmitter sends the values of scaling factors gm, gα, and gαDC that were obtained from the model I measurements with the reference receiver at blockofto the model J receiver.

While wirelessly transferring power from the model I transmitter to the model J receiver, measurement circuitryin the transmitter and measurement circuitryin the receiver may measure the operating parameters of the transmitter and receiver (e.g., coil currents and voltages, rectifier output voltage and current, etc.). Current and voltage measurements may, if desired, be exchanged between transmitter and receiver (e.g., using in-band wireless communications).

The information that is measured with circuitryandmay be used in conjunction with the exchanged scaling factors to compute PLOSSRX and PLOSSTX using equations 2b and 3b.